Dynamic spectrum access (DSA) and dynamic spectrum management (DSM) are terms that refer to systems and techniques for dynamically allocating spectral resources to users in an efficient manner. In some systems implementing DSA, individual communication devices may have the ability to monitor a spectral environment about the device and to adapt their transmit parameters (e.g., frequency, power, modulation, timing, etc.) to that environment in an efficient manner that ensures a desired level of communication quality. Cognitive radio systems are one example of communication devices that make use of DSA principles to make more efficient use of spectral resources and adapt to a changing electromagnetic environment.
In conventional systems implementing DSA, the spectral environment about a device is sensed during periods when a radio frequency (RF) transmitter within the device is idle. This is because signals transmitted from the RF transmitter will typically leak into the receiver front end and interfere with signal reception if spectral sensing and signal transmission are performed simultaneously. This interference can significantly disrupt the accuracy of the spectral sensing. Because sensing is not permitted during transmission, a conventional radio's knowledge of the wireless channel can be stale after a period of transmission. This fact sometimes requires relatively complex protocols to be used to ensure that fresh channel information is available to a radio. These protocols may require, for example, that fresh information be received from other sources and/or that partial channel information be used. Information from other sources is often of limited value as other nodes do not necessarily observe the channel in the same way that the radio of interest does. Likewise, partial channel information can be of limited value as it may not include the data needed to make quality decisions regarding transmit parameters. As will be appreciated, inaccurate, stale, or incomplete channel information can lead to collisions in the channel in a system implementing DSA.
There is a need for techniques for ensuring that fresh channel information is available within a radio implementing DSA. This may be accomplished by, for example, providing a radio that is capable of simultaneously transmitting RF signals and sensing an electromagnetic environment.